And there's more than enough space under the Model S hood to fit in a second motor. Right now, that space serves as the front trunk--which Tesla insists on calling a "frunk."

We think there's a strong chance that at some point over the next 18 months--perhaps this fall, for the long 2014 model year during which the Model X will not arrive--Tesla will announce a new all-wheel-drive option for the Model S.

We're not going to hazard any guesses about performance, pricing, or other options.